The present invention relates to a composition which is useful for performing liquid ion exchange chromatography in a packed column.
In Small et al U.S. Pat. No. 4,101,460, a high performance ion exchange composition is described which includes Component A, an insoluble synthetic resin substrate, having ion exchange sites on at least its available surface, and Component B, a finely divided synthetic resin particle of 0.1 to 5 microns median diameter, having ion exchange sites on their outer surfaces. Component B is irreversibly attached as a monolayer to Component A. While the lower limit of disclosed median diameter of Component B is 0.1 micron, the actual lowest median diameter disclosed in the examples is 0.6 micron. Referring to Tables II and III on columns 15 and 16 of the patent, the chromatographic separations with compositions of four different Component B median diameters are compared. The true resolution time (T.sub.2) illustrated in Table 3, decreases with a decrease in the median diameter down to a minimum at a median diameter of 0.95, but thereafter increases with a median diameter of 0.6. At column 16, lines 61-63, the best performing packing is stated to be the one which shows the shortest true resolution time, and so the packing with the Component B median diameter 0.95 is stated to be superior to one with a 0.6 micron median diameter. From this, it is logical to conclude that performance is optimized at a Component B median diameter above 0.6 micron.
Referring again to U.S. Pat. No. 4,101,460, at column 4, lines 15-25, it is stated that the composition may be varied by varying the size of Component B, specifically that the particle sizes with a large medium diameter produce an ion exchange composition with high capacity and low performance, relative to an ion exchange composition prepared from a particle sample with a relatively smaller mean diameter. There is no suggestion of any benefit to be obtained by the use of differently sized Component A particles.